To　examine　how　the　rates　and　pathways　of　anaerobic　organic　carbon　mineralization　(AOCM)　of　tidal　freshwater　wetlands　change　with　low-level　increases　in　salinity,　we　investigated　the　rates　and　controls　of　microbial　iron　and　sulfate　reduction,　methane　production,　and　total　AOCM　in　tidal　wetlands　along　a　freshwater　to　oligohaline　(0.1–3.3　ppt)　gradient　in　the　Min　River　Estuary　in　southeastern　China.　Porewater　chloride　was　found　to　be　strongly　correlated　with　total　organic　carbon　(TOC),　carbon　to　nitrogen　(C:N)　ratios,　and　porewater　geochemistry　(sulfate,　pH,　ammonium,　and　dissolved　methane　levels).　Furthermore,　a　higher　plant　biomass,　larger　iron　oxides　pool,　and　lower　sulfide　levels　were　observed　in　the　oligohaline　wetlands.　The　contribution　of　microbial　sulfate　reduction　to　AOCM　increased　from　16%　to　67%.　In　contrast,　the　contribution　of　microbial　iron　reduction　and　methane　production　declined　from　52%　to　22%　and　12%　to　2%,　respectively,　along　the　increasing　salinity　gradient.　No　consistent　changes　were　found　in　the　total　AOCM　rates.　The　rates　of　methane　production　were　primarily　controlled　by　the　C:N　ratios　and　concentrations　of　porewater　ammonium　and　amorphous　iron　oxides,　while　the　microbial　sulfate　and　iron　reduction　rates　were　mainly　controlled　by　belowground　biomass,　water　content,　and　concentrations　of　porewater　chloride　and　sulfate.　Our　findings　provide　insight　into　the　potential　consequences　of　modest　saltwater　intrusion;　these　may　not　alter　the　rates　of　AOCM　in　the　Min　River　Estuary,　but　could　change　the　dominant　AOCM　pathway　from　microbial　iron　reduction　to　sulfate　reduction　and　accelerate　sulfidic　effects　in　this　historically　freshwater　wetland　ecosystem.　©　2018　Elsevier　B.V.